Originally Posted By kentj340
The process that made the "splotchy" dark and light areas, called spangles, still exists big time. The spangles were produced on a high volume, continuous hot dip galvanizing line at a coated sheet mill. The sheet was then shipped to a stamping shop that made the part.

Back in the muscle car days, it was normal to make the galvanized steel sheet with very large spangles, because most customers preferred an appearance that was easily recognized as galvanized sheet rather than uncoated steel sheet.

Nowadays large spangles are not produced as much, and galvanized sheet is usually smaller 'regular spangle', 'min spangle', or 'zero spangle'.

Sometimes you can see large spangles on such things as traffic signal poles that are hot dip galvanized in a batch process rather than on a high speed line.

https://www.youtube.com/watch?v=X9nAtO7Oof8


All true information and would like to add that galvanizing of years past was a mix of metals, the largest of which is zinc, the primary 2nd material was lead. Todays mix is zinc and nickel, and the reason galvanizing is much more flashy that spangle in the 70's. As memory serves nickel replaced lead in the 90's and came with issues, mainly the increased reflectivity for things like lamp posts or items used on an airport runway. To dull it a bit they use an acid solution for items requiring lower sheen.
Hot dip and sheet processing may be similar but the results usually vary. Hot dip platers usually don't like working with thin gauge car sheetmetal and will usually tell you they are not responsible for damage, they are set up for large jobs like lamp posts and other large industrial structure. Additionally the dip process produces a large buildup edge where material accumulates as the part is removed from the dip. I had some parts dipped, first by using an excess piece to see results. The dip house I went to had a salesmen with a car soft spot and really worked to help get as good of results as possible by blowing the lower edge of the parts as they were removed from the dip, helping to eliminate the buildup. They then did the acid dip to reduce the flashy surface finish. While you cannot get perfection relative to the sheet process its the only option you have as once formed the controlled sheet process cannot be performed. Throw in the lead Vs nickel of the old Vs current process and you can only match so close, even with the acid dip. I'm happy with the parts I had done as they are protected and carry the correct material . . . so to speak.